Hybrid hydride abstraction

The dication 212+ composed of two methylium units connected to a p-phenylene spacer would be a candidate for new Wurster type violene-cyanine hybrid (Figure 12) (15). The reaction of four molar amounts of azulene 6b with terephthalaldehyde yielded the hydro precursor. Synthesis of the dication 212+ was accomplished by hydride abstraction with DDQ in almost quantitative yield. The dication 212+ was expected to show destabilization, but instead it exhibited high thermodynamic stability just like the corresponding monocation 3b+. 

Synthesis of the tetracation 314+ was accomplished by hydride abstraction on the corresponding tetrahydro derivative, analogous to other tetracations. CV and DPV measurements demonstrated that tetracation 314+ exhibits a two-step reduction as presumed for a cyanine-cyanine hybrid. This indicates that the redox interaction among the four cationic units is increased by the anthraquinodimethane core. 

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